I believe they were the highest decorated unit. They served in the Italian campaign.
"The 442nd/100th sustained 9,486 wounded and over 600 killed suffered, the highest casualty rate of any American unit during the war. For their heroism, the men of the 442nd/100th won fifty-two Distinguished Service Crosses, 560 Silver Stars and the Congressional Medal of Honor was awarded posthumously to Pfc. Sadao Munemori. The 442nd Regimental Combat Team also won seven coveted Presidential Unit Citations for its performance. The men in the 100th Battalion alone had earned 900 Purple Hearts, thirty-six Silver Stars, twenty-one Bronze Stars, and three Distinguished Service Crosses."
http://www.marauder.org/nisei02.htm